Traditionally, most plastic molding machine automation solutions consist of at least two distinct elements. The first element is a dedicated programmable logic controller (“PLC”) which controls the real-time digital and analog functions of the machine. The PLC typically stores and executes a control program to control various input/output (“I/O”) devices and thereby control the operational sequences of the I/O devices. The second element is a human machine interface (“HMI”) which allows the operator to change and view the processes of the machine. The HMI is usually in the form of an operator station, which runs software that allows the operator to control the machine's functions.
There are drawbacks associated with the traditional plastic molding machine solution is many. First, the PLC has relatively limited processing power. The limited processing power or processing speed of the PLC may prevent the optimal efficient operation of the molding machine. Second, PLC technology is typically proprietary to the manufacturer of the PLC and upgrading and maintaining the PLC is typically at the whim of the PLC manufacturers. Thirdly, the process control program is typically written in arcane and complex low level language. Purchasers and other end users of PLCs must be trained to make even minor modifications to the control programs.
Aside from these two key elements, a plastic molding machine may also include a dedicated motion controller to provide real-time servo control. In some instances, the functionality of the motion controller may be included in the PLC. Additionally, a plastic molding machine may include temperature control. Stand-alone dedicated temperature controller may provide this functionality or it may be included in the PLC. Other I/O devices may further be included in the plastic molding machine, primarily dependent upon whether the plastics molding machine is used to support extrusion, injection molding, blow molding or thermoforming.
Information exchange between the operator station and the machine control traditionally has been done via a data network. Examples of the data network would be Profibus, Ethernet and other serial data networks. However, using this type of communication path introduces data latencies between the machine control (PLC functions) and the operator station (HMI functions). Furthermore, on plastic molding machines particularly, it is necessary to pull large quantities of data from the PLC to the operator station. For example, in blow molding machines, it is necessary to quickly download and upload the parison set point and actual value tables between the PLC and the HMI.
Therefore, there is a need for a plastic molding machine automation solution which can reduce the latencies involved in communication between the PLC and the HMI over a data network so that the plastic molding machine can operate at a more efficient speed.